The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board (PCB) attached to a disk drive base of the HDA. The head disk assembly includes at least one disk (such as a magnetic disk, magneto-optical disk, or optical disk), which is clamped to a rotating hub of a spindle motor. A head stack assembly (HSA) is actuated to position heads adjacent the major surfaces of the disk(s), to read and write information stored thereon. The printed circuit board assembly includes electronics and firmware for controlling the rotation of the spindle motor, for controlling the actuation and position of the HSA, and for providing a data transfer channel between the disk drive and its host.
The head stack assembly typically includes an actuator, at least one head gimbal assembly (HGA), and a flex cable assembly. Each HGA includes a head for reading and writing data from and to an adjacent disk surface. In magnetic recording applications, the head typically includes an air bearing slider and a magnetic transducer that comprises a writer and a read element. The magnetic transducer's writer may be of a longitudinal or perpendicular design, and the read element of the magnetic transducer may be inductive or magnetoresistive. In optical and magneto-optical recording applications, the head may include a minor and an objective lens for focusing laser light on an adjacent disk surface.
The spindle motor typically includes the rotating hub (on which annular disks are mounted and clamped), a magnet attached to the hub, and a stator. Various coils of the stator are selectively energized to form an electromagnetic field that pulls/pushes on the magnet, thereby rotating the hub. Rotation of the spindle motor hub results in rotation of the mounted disks.
Many contemporary disk clamps are attached to the spindle motor hub by screws that are arranged in a circle around the spindle motor shaft (e.g. a non-rotating shaft). When the screws are tightened, they cause the clamping pressure to be non-uniform, such that the regions near each screw exert higher clamping pressure and the areas between the screws exert lower clamping pressure. Such non-uniform clamping pressure may produce an undesirably large sinusoidal warping of the clamped disk(s). The resulting curvature of the disk surface is known as “disk crown”.
Disk crown due to non-uniform clamping can modulate and affect the microscopic spacing between the disk surface and the adjacent read/write head. Such microscopic spacing affects the performance of the head in reading and writing, and so excessive disk crown can adversely affect the performance and signal to noise ratio (SNR) associated with disk drive operations. Therefore, there is a need in the art for a disk drive design having a disk clamp that exerts a more uniform clamping pressure on the disk(s).
The screws that attach a contemporary disk clamp to the spindle motor hub typically do not force the disk clamp to lie flat against a top surface of the spindle motor hub in the region around each screw. There is a good reason why; in many designs some finite vertical or tilt clearance between the clamp and the top surface of the spindle motor hub may be required so that the torque on the screws can vary the clamping pressure applied to the annular disk. However, it may be desirable to decrease the sensitivity of clamping pressure on screw torque, for example to decrease manufacturing variation in clamping pressure. Therefore, there is a need in the art for a disk drive design having a disk clamp that can reduce the sensitivity of clamping pressure on screw torque.
Also, some particulate and other contamination may escape from the screws and screw holes in the spindle motor hub, via the previously described finite vertical or tilt clearance between the clamp and the top surface of the spindle motor hub. Such contaminants, if excessive, may cause head crash or otherwise decrease the reliability of the disk drive if they spread within the head disk assembly (e.g. by being spun off by the centrifugal force associated with spindle hub rotation). Therefore, there is a need in the art for a disk drive design having a disk clamp that can better contain contamination that may escape from the screws and screw holes in the spindle motor hub.